Liquid crystal displays (LCD) have many advantages such as thin body, low power consumption and no radiation. They have been widely used, such as mobile phones, personal digital assistants (PDA), digital cameras, computer screens and laptop screens.
Organic Light-Emitting Diode (OLED) displays, also known as organic electroluminescent displays, are an emerging type of flat panel display device, due to its simple preparation process, low cost, low power consumption, high brightness, wide operating temperature range, thin, fast response, easy to achieve color display and large screen display, easy to implement and integrated circuit driver to match, easy to achieve the advantages of flexible display, which has broad application prospects.
According to the driving mode, the OLEDs can be divided into two types: a passive matrix OLED (PMOLED) and an active matrix OLED (AMOLED), namely direct addressing and thin film transistor (TFT) matrix addressing two categories. Wherein, AMOLED has a matrix arrangement of pixels, belonging to the active display type, high luminous efficiency, usually used for high-definition large-size display device.
Thin Film Transistors (TFTs) are the main driving elements in liquid crystal display devices and active matrix OLED display devices, and are directly related to the development direction of high-performance flat panel display devices. The thin film transistor has a variety of structures. The thin film transistor having a corresponding structure also has a variety of materials. Amorphous silicon (a-Si) is a more common material. However, as liquid crystal display devices and OLED display devices have been developed toward large size and high resolution, the mobility of the traditional a-Si is about 1 cm2/(VS) and has been unable to meet the requirements, the metal oxide represented by indium gallium zinc oxide (IGZO) has a mobility of more than 10 cm2/(Vs). Moreover, the preparation of the corresponding thin film transistor is compatible with the existing a-Si semiconductor-driven thin film transistor line and has rapidly become the focus of research and development in the field of display in recent years.
Top-Gate Self-Aligned Oxide Semiconductor TFTs are a common type of TFT in OLED panels, in the manufacturing process of the top-gate self-aligned oxide semiconductor TFT, it is usually necessary to cover the oxide semiconductor layer and the gate with an Inter Layer Dielectric (ILD). The material of the inter layer dielectric is generally selected from silicon nitride (SiNx) and silicon oxide (SiOx). Since the chemical vapor deposition process of silicon nitride needs to introduce ammonia (NH3), ammonia easily introduces too much hydrogen into the oxide semiconductor layer, resulting in the deterioration of the performance of the oxide semiconductor layer. Therefore, in general, a silicon oxide material is selected in the art to form an inter layer dielectric, avoiding introduction of excessive hydrogen element in the oxide semiconductor layer. However, since the CVD process of silicon oxide needs to introduce nitrous oxide (N2O), the nitrous oxide is easy to oxidize the copper metal on the gate surface to cause abnormal performance of the TFT device.